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ftpserver.pl: three new custom FTP server commands to disable data channel

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NODATACONN421: applies only to active FTP mode, instructs server to not
establish data connection back to client and reply with FTP 421.

NODATACONN425: applies only to active FTP mode, instructs server to not
establish data connection back to client and reply with FTP 425.

NODATACONN: applies to both active and passive FTP modes, instructs server
to not establish nor accept a data channel and fool client into believing
that the data channel connection is possible.

Some polishing probably required.
This commit is contained in:
Yang Tse 2011-10-27 21:46:24 +02:00
parent ddeab48245
commit c761fcb055
1 changed files with 77 additions and 23 deletions
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64
tests/ftpserver.pl
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@ -132,6 +132,9 @@ my $retrweirdo; # set if ftp server should use RETRWEIRDO
my $retrnosize; # set if ftp server should use RETRNOSIZE
my $pasvbadip; # set if ftp server should use PASVBADIP
my $nosave; # set if ftp server should not save uploaded data
my $nodataconn; # set if ftp srvr doesn't establish or accepts data channel
my $nodataconn425; # set if ftp srvr doesn't establish data ch and replies 425
my $nodataconn421; # set if ftp srvr doesn't establish data ch and replies 421
my %customreply; #
my %customcount; #
my %delayreply; #
@ -1071,7 +1074,7 @@ sub PASV_ftp {
logmsg "failed to run sockfilt for data connection\n";
killsockfilters($proto, $ipvnum, $idnum, $verbose, 'data');
sendcontrol "500 no free ports!\r\n";
return 0;
return;
}
logmsg "Run sockfilt for data on pid $slavepid\n";
@ -1102,6 +1105,12 @@ sub PASV_ftp {
$pasvport = $2;
}
if($nodataconn) {
# kill data sockfilter and make believe the client
# that it is possible to establish a data connection.
killsockfilters($proto, $ipvnum, $idnum, $verbose, 'data');
}
if($cmd ne "EPSV") {
# PASV reply
my $p=$listenaddr;
@ -1117,6 +1126,11 @@ sub PASV_ftp {
sendcontrol sprintf("229 Entering Passive Mode (|||%d|)\n", $pasvport);
}
if($nodataconn) {
logmsg "client fooled, running without data connection\n";
return;
}
eval {
local $SIG{ALRM} = sub { die "alarm\n" };
@ -1162,13 +1176,16 @@ sub PORT_ftp {
my $port;
my $addr;
# kill previous data connection sockfilt when alive
killsockfilters($proto, $ipvnum, $idnum, $verbose, 'data');
# We always ignore the given IP and use localhost.
if($cmd eq "PORT") {
if($arg !~ /(\d+),(\d+),(\d+),(\d+),(\d+),(\d+)/) {
logmsg "bad PORT-line: $arg\n";
sendcontrol "500 silly you, go away\r\n";
return 0;
return;
}
$port = ($5<<8)+$6;
$addr = "$1.$2.$3.$4";
@ -1178,7 +1195,7 @@ sub PORT_ftp {
if($arg !~ /(\d+)\|([^\|]+)\|(\d+)/) {
logmsg "bad EPRT-line: $arg\n";
sendcontrol "500 silly you, go away\r\n";
return 0;
return;
}
sendcontrol "200 Thanks for dropping by. We contact you later\r\n";
$port = $3;
@ -1186,12 +1203,31 @@ sub PORT_ftp {
}
else {
sendcontrol "500 we don't like $cmd now\r\n";
return 0;
return;
}
if(!$port || $port > 65535) {
print STDERR "very illegal PORT number: $port\n";
return 1;
return;
}
if($nodataconn) {
# don't establish data connection back to client,
# and don't send anything over control connection.
logmsg "client fooled, will not connect back to him\n";
return;
}
elsif($nodataconn425) {
# don't establish data connection back to client,
# reply with 425 over control connection.
sendcontrol "425 Can't open data connection\r\n";
return;
}
elsif($nodataconn421) {
# don't establish data connection back to client
# reply with 421 over control connection.
sendcontrol "421 Connection timed out\r\n";
return;
}
# We fire up a new sockfilt to do the data transfer for us.
@ -1230,6 +1266,9 @@ sub customize {
$retrnosize = 0; # default is no use of RETRNOSIZE
$pasvbadip = 0; # default is no use of PASVBADIP
$nosave = 0; # default is to actually save uploaded data to file
$nodataconn = 0; # default is to establish or accept data channel
$nodataconn425 = 0; # default is to not send 425 without data channel
$nodataconn421 = 0; # default is to not send 421 without data channel
%customreply = (); #
%customcount = (); #
%delayreply = (); #
@ -1271,6 +1310,21 @@ sub customize {
logmsg "FTPD: instructed to use PASVBADIP\n";
$pasvbadip=1;
}
elsif($_ =~ /NODATACONN425/) {
# applies only to active FTP mode
logmsg "FTPD: instructed to use NODATACONN425\n";
$nodataconn425=1;
}
elsif($_ =~ /NODATACONN421/) {
# applies only to active FTP mode
logmsg "FTPD: instructed to use NODATACONN421\n";
$nodataconn421=1;
}
elsif($_ =~ /NODATACONN/) {
# applies to both active and passive FTP modes
logmsg "FTPD: instructed to use NODATACONN\n";
$nodataconn=1;
}
elsif($_ =~ /NOSAVE/) {
# don't actually store the file we upload - to be used when
# uploading insanely huge amounts